Boring mill machine tool used to increase the size of a hole previously made in a work piece, usually with the purpose of obtaining a required degree of finish and accuracy in the final hole. In a horizontal boring mill the work piece is held stationary on a vertical table whose position can be adjusted. A spindle attached to a vertically adjustable head holds the cutting tool, which is fed horizontally into the work. In a vertical boring mill the work piece is made to revolve on a horizontal circular table as the tool is fed in.